In the field of data processing, a common paradigm is to provide a racking framework into which are mounted a plurality of similar replaceable data processing, storage, or other digital data handling units. The replaceable units are typically arranged in a series of adjacent vertically repeating mounting locations in the racking framework. Typically, in a data processing environment, such racks are of standardized 19 inch format in which the slots for insertion of replaceable units are 19 inches (482.6 mm) wide. The height of the replaceable units is measured in rack units, or U, where 1 U is 1.75 inches (44.45 mm). A typical full height rack may be over 6 feet (1.8 m) in height and comprise 42 U of equipment, so 42 1 U units, or 21 2 U units for example.
In one arrangement a number of substantially identical individual removable digital data handling units may be positioned one above another. In another arrangement, a number of enclosures, for example 7 U in height, may be mounted in a rack. Each enclosure provides mounting locations for a number of identical vertically mounted digital data handling units, such as data processing units, for example blade servers. Other arrangements may include, for example, an enclosure having mounting locations for a number of vertically or horizontally arranged disk drives.
A trend over recent years has been for the removable digital data handling units to be made progressively smaller, so that more units may be fitted into a given rack framework. Whilst this provides for more economical use of rack space, it may lead to problems when individual units which fail need to be removed. Little frontal space is available on the removable digital data handling units for such things as status indication light emitting diodes (LEDs), sockets for wiring, and hand engageable elements, for example handles for removal, or handles including mechanisms for unlocking and removal, of the individual unit. It is consequently becoming easier for an operator to see an LED indicator showing a failure in a removable unit, for example, but to remove an adjacent or other unit in error by, for example, operating the wrong release handle. Such an error may have serious consequences in loss of data resulting from the interruption of data communication with a still operating replaceable unit.
It would be advantageous to provide a means to facilitate removal of the correct removable unit when a failure is identified.